Google employees ride their Google multi-colored bicycles to and from the GooglePlex along Charleston Road in Mountain View, Tuesday, June 24, 2014. Large and small, buildings are being collected in Mountain View by Google, which is on a shopping spree for parcels near -- and sometimes not so near -- its headquarters in Mountain View. (Patrick Tehan/Bay Area News Group)

MOUNTAIN VIEW — As America’s giant tech companies scramble to extend their reach ever further into our homes and wallets, the battle between Google and Amazon has taken a bitter turn.

Google announced Dec. 5 that it would yank its video-streaming service YouTube from Amazon’s Fire TV device and Echo Show smart-speaker with screen. The change for Echo Show takes place immediately, while YouTube is to come off Fire TV — which enables streaming of TV shows and movies — on Jan. 1.

​“We’ve been trying to reach agreement with Amazon to give consumers access to each other’s products and services,” a Google spokesperson said in a statement Dec. 5.

However, the spokesperson said, Amazon doesn’t carry Google’s Chromecast streaming device or its Google Home virtual assistant, or allow users of the Google Cast browser extension to access Amazon Prime Video. And Amazon last month stopped selling some products from Nest, a Google spin-off that remains under Google’s parent firm Alphabet.

“Given this lack of reciprocity, we are no longer supporting YouTube on Echo Show and FireTV,” the Google spokesperson said. “We hope we can reach an agreement to resolve these issues soon.”

Amazon did not immediately respond to a request for comment.

The move marks the second time Google has pulled YouTube from the Echo Show, having done it once from September into November, alleging that Amazon had violated YouTube’s terms of service by running it on the Show device and “creating a broken user experience,” according to media reports from September.

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Both Google and Amazon have in recent years started going after new markets. The rival firms have been competing furiously with virtual-assistance devices, and in cloud storage and processing. Now, Amazon looks to be making inroads into Google’s bread and butter: digital advertising.

According to a new report, three of the world’s largest advertising agencies intend to boost their ad spending with Amazon to more than $800 million together, a substantial increase.

Ad agency WPP will spend about $200 million for ads on Amazon platforms this year, and may increase that spending by up to 50 percent next year, the Wall Street Journal reported. Another major ad firm, Publicis, plans to increase its spending on Amazon by about 50 percent next year, to $300 million from around $200 million, according to the paper. Omnicom, which spends about $100 million a year with Amazon, could double that amount next year and continue to escalate its spending for ads on Amazon into the future, the WSJ reported.

Google and Facebook are widely seen as digital advertising’s duopoly. Between the two of them, they are expected to haul in 63 percent of U.S. investment in digital ads this year, according to eMarketer.